With 1,210,193,422 residents reported in the 2011 provisional census report, India is the world's second-most populous country. Its population grew by 17.64% during 2001–2011, compared to 21.54% growth in the previous decade (1991–2001). The human sex ratio, according to the 2011 census, is 940 females per 1,000 males. The median age was 24.9 in the 2001 census. The first post-colonial census, conducted in 1951, counted 361.1 million people. Medical advances made in the last 50 years as well as increased agricultural productivity brought about by the "Green Revolution" have caused India's population to grow rapidly. India continues to face several public health-related challenges.

Life expectancy in India is at 68 years, with life expectancy for women being 69.6 years and for men being 67.3. There are around 50 physicians per 100,000 Indians. The number of Indians living in urban areas has grown by 31.2% between 1991 and 2001. Yet, in 2001, over 70% lived in rural areas. The level of urbanisation increased from 27.81% in 2001 Census to 31.16% in 2011 Census. The slowing down of the overall growth rate of population was due to the sharp decline in the growth rate in rural areas since 1991. According to the 2011 census, there are 53 million-plus urban agglomerations in India; among them Mumbai, Delhi, Kolkata, Chennai, Bangalore, Hyderabad and Ahmedabad, in decreasing order by population. The literacy rate in 2011 was 74.04%: 65.46% among females and 82.14% among males. The rural urban literacy gap which was 21.2 percentage points in 2001, dropped to 16.1 percentage points in 2011. The improvement in literacy rate in rural area is two times that in urban areas. Kerala is the most literate state with 93.91% literacy; while Bihar the least with 63.82%.

India is home to two major language families: Indo-Aryan (spoken by about 74% of the population) and Dravidian (spoken by 24% of the population). Other languages spoken in India come from the Austroasiatic and Sino-Tibetan language families. India has no national language. Hindi, with the largest number of speakers, is the official language of the government. English is used extensively in business and administration and has the status of a "subsidiary official language"; it is important in education, especially as a medium of higher education. Each state and union territory has one or more official languages, and the constitution recognises in particular 22 "scheduled languages". The Constitution of India recognises 212 scheduled tribal groups which together constitute about 7.5% of the country's population. The 2011 census reported that the religion in India with the largest number of followers was Hinduism (79.8% of the population), followed by Islam (14.23%); the remaining were Christianity (2.30%), Sikhism (1.72%), Buddhism (0.70%), Jainism (0.36%) and others (0.9%). India has the world's largest Hindu, Sikh, Jain, Zoroastrian, and Bahá'í populations, and has the third-largest Muslim population—the largest for a non-Muslim majority country.